Composite building panels such as drywall panels or cement board are frequently used to enhance construction productivity by reducing time spent waiting for hydraulic materials to set and dry. Conventional drywall panels, which are primarily made of gypsum, are particularly useful for interior construction of walls and ceilings. Gypsum panels are also available with water resistant additives that allow them to be used in damp or humid areas like bathrooms or basements. Precast cement board is useful where strength or stability is desired, such as an underlayment for ceramic tile. A wide variety of these building panels are available that utilize a variety of compositions for specific locations or applications.
Many building panels are constructed with facing or reinforcing materials on one or more faces of the panel. Facing materials are commonly used to alter one or more physical properties of the panel. In the case of drywall, the material on the face exposed after installation provides a smooth surface that is receptive of decorative coatings such as paint or wallpaper. Reinforcing of the edge with facings provides strength where panels are nailed into place. Cement board panels utilize facings that hold fast to adhesives, both to hold the panel in place and to tightly bond the panel to decorative finishes such as flooring tiles.
Less frequently, facing materials have been used to cover the edges of a composite building panel. In U.S. Pat. No. 1,787,163, fabric is used to reinforce the longitudinal edge of the panel to improve nailing durability and other structural qualities of the edge. The use of facings also helps to protect the panel from gouges, chipping, nicks and other damage that may occur during shipping, stocking or installation of the panels. The edge strip fabric was described as being sufficiently porous to allow the plaster to penetrate through it.
U.S. Pat. Nos. 6,187,409 and 6,488,792 reveal the use of a U-shaped edge strip comprising reinforcing fibers. The strip has permeable portions that adhere to the top and bottom surface of the panel. Along the longitudinal face there is an impermeable portion that does not adhere to the cementitious core. In practice, however, it is very difficult to align the impermeable portion exactly with the longitudinal face. This results in panels where the impermeable portion extends over the top or bottom edge of the longitudinal face, leaving the opposing edge on the longitudinal face covered with the water permeable covering. As the slurry permeates the covering, it comes through to the surface of the longitudinal face producing a non-uniform and blotchy look along the longitudinal face when the finished panels are stacked for storage. Where the slurry has permeated the edge strip and dried, the surface is rough and uneven, resulting in an edge that is uncomfortable to grasp with hands.